What is a characteristic of a virus?

A defining characteristic of a virus is that it infects a system when executed by the user. This means that viruses typically require some form of user interaction, such as opening an infected file or executing a compromised program, to begin their replication process. Once activated, the virus can spread to other files and systems without requiring further direct user action, but the initial infection depends on user execution.

While some malicious software does not require user action to replicate, that trait is more applicable to worms. A virus fundamentally relies on user execution to enter and replicate within a system. The notion that it runs with user consent is misleading; viruses generally take advantage of unsuspecting users and are not authorized actions by the user. Additionally, stating that a virus solely exists in the cloud is inaccurate, as viruses are typically found in executable files and cannot exist without a host on a local machine or network environment where they can execute and replicate.